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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-4 To Explore Further This presentation gives a brief idea about electrostatic microactuators. So if you want to know more about this topic, you can try searching IEEE Xplore where you can find about current research going in this field. IEEE Xplore Another type of MEMS actuator is electromagnetic microactuators. You may also want to explore them.explore

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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-9 Working (cont.) 1 The comb-drive-type electrostatic microactuator has a large numbers of fine interdigitated “fingers” to generate the actuated force. A comb drive that is actuated by a parallel-plate field at each finger pair is called a “transverse” comb drive. The movable plate and movable finger are suspended by mechanical elastic members.

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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-12 Working (cont.) 1 In the above figure x is the displacement of the movable fingers from the equilibrium position. This comb drive is said to be “offset” since the distance x 1 is much smaller than the distance x 2. Each gap between adjacent fingers has a specific capacitance.

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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-13 Working (cont.) 1 For instance, C 1 and C 2 can be calculated by the following: where K d = dielectric constant for the material, ε = permittivity of free space, and A = overlapping area of each finger pair.

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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-14 Working (cont.) 1 The electrostatic force on the movable comb fingers is given by where N = number of parallel capacitor pairs, and V = applied actuation voltage.

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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-15 Fabrication 2 The following slides show the fabrication process of an electrostatic microactuator for optical shutter (shown below) application.

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5/5/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-24 Limitations Apart from advantages of high performance and low cost, these microactuators have some limitations also: In parallel-plate type microactuators, the force output is highly nonlinear over stroke range and may become unstable under large actuation voltages. Electrical isolation is another problem in parallel- plate microactuators.